ARMY AL&T
It is crucial to test the vehicle in representative conditions and observe the response to ensure the vehicle meets the requirement.
What does this mean for the test and evaluation community? How does this impact ongoing or future test programs?
Te types of tests conducted on our tactical and combat ground vehicles are vast with varying levels of influence by ambient temperature. For instance, determining a vehicle’s roll-over tipping point on a tilt table is completely unrelated to the ambi- ent temperature during the test. Te tests most impacted by the change in ambient temperature are those that will require peak engine power and torque during mobility-performance testing.
Mobility-performance testing is predominately evaluated by three different tests: 1) Vehicle top speed; 2) Max grade hill climb; and 3) Full-load cooling. Te outcomes of these tests tell the Army the vehicles’ maximum traveling speed, the steepest grade it can climb and how much torque it can produce without overheating to the point of engine damage.
Te Army needs to run these three tests at 120 degrees to guar- antee that electronically controlled powertrains will deliver the performance advertised by the manufacturer. Tis means that tests will need to be scheduled both geographically and season- ally in order to ensure this ambient temperature is reached. If this is not possible outdoors at a test range because of test program schedule constraints, the test needs to be performed in a labora- tory with environmental control and dynamometers.
CONCLUSION As technology continues to advance in order to ensure that the United States warfighter has superior advantage, military vehi- cles will continue to gain in complexity and sophistication. When evaluating vehicles with electronically controlled powertrains, linear extrapolation of powertrain fluids can introduce significant error during mobility-performance testing or deliver completely invalid results.
For conducting mobility-performance testing at the upper requirement for ambient temperature (120 degrees), the test program can be supplemented with laboratory testing. Tis is not just about simple cost savings. Most likely, there is a slight cost savings to running tests in the environmental chamber over the proving ground. Te point is that we pay a great deal of money for testing that may be bogus. People think that linear extrapo- lation reduces costs, and therefore they can test anywhere in the United States at any temperature. Freedom in exchange for useless results—or results that harm the chances of a vehicle the Army wants and needs in passing a test—is a terrible bargain. If you evaluate cost savings for testing in seasonally and geographically appropriate areas to actually have 120 degrees, environmental chamber testing would probably be a huge savings. But that proposition remains to be tested, because up to this point we as a test community have not been willing to limit ourselves to test at 120 and instead insist on extrapolation.
Within the laboratory environment, the ambient temperature can be controlled to produce representative responses from the vehicle’s powertrain. However, laboratory testing cannot be seen as a replacement for field testing as other vehicle systems such as wheels or tracks or suspension are not being exercised. Using both field and laboratory testing is necessary to comprehensively eval- uate vehicles with electronically controlled powertrains.
For more information, view the comprehensive cal paper in DTIC (AD1170619) or
techni- contact the authors,
steven.m.zielinski2.civ@
army.mil and
paul.b.maguire4.civ@
army.mil.
STEVEN ZIELINSKI is a technical specialist for Ground Vehicle Power and Mobility - Test and Evaluation team at the Ground Vehicle Systems Center (GVSC). He holds an M.S. in mechanical engineering from Wayne State University and a B.S. in engineering physics from Oakland University. He holds the DAWIA Practitioner certification in engineering and technical management.
PAUL MAGUIRE is a technical specialist for Ground Vehicle Power and Mobility - Test and Evaluation team at GVSC. He holds an M.S. in mechanical engineering and a B.S. in chemical engineering, both from Wayne State University. He earned his Professional Engineering license in mechanical engineering in 2006. He holds the DAWIA Practitioner certification in engineering and technical management.
https://asc.ar my.mil
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